High contrast development of lithographic films has been carried out for many years using special developers which are known in the art as "lith" developers. In conventional "lith" developers, high contrast is achieved using the "lith effect" (also referred to as infectious development) as described by J. A. C. Yule in the Journal of the Franklin Institute, Vol. 239, 221-230, (1945). This type of development is believed to proceed autocatalytically. To achieve "lith effect" development, a low, but critical, concentration of free sulfite ion is maintained by use of an aldehyde bisulfite adduct, such as sodium formaldehyde bisulfite, which, in effect, acts as a sulfite ion buffer. The low sulfite ion concentration is necessary to avoid interference with the accumulation of developing agent oxidation products, since such interference can result in prevention of infectious development. The developer typically contains only a single type of developing agent, namely, a developing agent of the dihydroxybenzene type, such as hydroquinone.
Conventional "lith" developers suffer from serious deficiencies which restrict their usefulness. For example, the developer exhibits low capacity as a result of the fact that it contains hydroquinone as the sole developing agent. Also, the aldehyde tends to react with the hydroquinone to cause undesirable changes in development activity. Furthermore, the low sulfite ion concentration is inadequate to provide effective protection against aerial oxidation. As a result, a conventional "lith" developer is lacking in stability and tends to give erratic results depending on the length of time that it has been exposed to the air.
An alternative to the use of conventional "lith" developers is disclosed in Nothnagle, U.S. Pat. No. 4,269,929, "High Contrast Development Of Photographic Elements", issued May 26, 1981, the disclosure of which is incorporated herein by reference. As described in this patent, high contrast development of photographic elements is carried out in the presence of a hydrazine compound with an aqueous alkaline developing solution which has a pH of about 10 and below 12 and contains a dihydroxybenzene developing agent, a 3-pyrazolidone developing agent, a sulfite preservative, and a contrast-promoting amount of an amino compound. The developing solution combines the advantages of high capacity, a high degree of stability, and a long effective life, while providing excellent contrast and speed characteristics.
In this art, the hydrazine compounds are typically referred to as "nucleators" or "nucleating agents" and the amino compounds which function to enhance contrast are referred to as "boosters".
U.S. Pat. No. 4,269,929 describes the use of a very wide variety of amino compounds as contrast-promoting agents. In particular, it discloses the use of both inorganic amines, such as the hydroxylamines, and organic amines, including aliphatic amines, aromatic amines, cyclic amines, mixed aliphatic-aromatic amines, and heterocyclic amines. Primary, secondary and tertiary amines, as well as quaternary ammonium compounds, are included within the broad scope of the disclosure.
While the invention of U.S. Pat. No. 4,269,929 represents a very important advance in the art, its commercial utilization has been hindered by the disadvantageous characteristics exhibited by many amino compounds. Thus, for example, some amines suffer from the problem of toxicity, some from the problem of excessive volatility, some are characterized by highly unpleasant odors, some tend to form azeotropes with water, some exhibit an inadequate degree of solubility in an aqueous alkaline photographic developing solution, and some are costly yet must be used at a relatively high concentration such that they constitute a substantial portion of the total cost of the developing solution. Moreover, many amines exhibit a degree of activity as contrast-promoters in the method and composition of U.S. Pat. No. 4,269,929 that is less than is desired for commercial operation.
High contrast developing compositions which contain amino compounds as "boosters" and are intended for carrying out development in the presence of a hydrazine compound are also disclosed in U.S. Pat. Nos. 4,668,605 issued May 26, 1987 and 4,740,452 issued Apr. 26, 1988 and in Japanese Patent Publication No. 211647/87 published Sept. 17, 1987. U.S. Pat. No. 4,668,605 describes developing compositions containing a dihydroxybenzene, a p-aminophenol, a sulfite, a contrast-promoting amount of an alkanolamine comprising an hydroxyalkyl group of 2 to 10 carbon atoms, and a mercapto compound. The developing compositions of U.S. Pat. No. 4,740,452 contain a contrast-promoting amount of certain trialkyl amines, monoalkyl-dialkanolamines or dialkylmonoalkanol amines. The developing compositions of Japanese Patent Publication No. 211647/87 contain a dihydroxybenzene developing agent, a sulfite and certain amino compounds characterized by reference to their partition coefficient values. However, the developing compositions of U.S. Pat. Nos. 4,668,605 and 4,740,452 and Japanese Patent Publication No. 211647/87 do not fully meet the needs of this art, as they exhibit many disadvantageous characteristics. These include the need to use the contrast-promoting agent in such large amounts as to add greatly to the cost of the process and the many difficult problems that stem from the volatility and odor-generating characteristics of amino compounds that are effective to enhance contrast.
The inherent disadvantages of incorporating amino compounds as "boosters" in developing compositions have been recognized in the prior art, and proposals have been made heretofore to overcome the problems by incorporating the amino compound in the photographic element. In particular, the use of amino compounds as "incorporated boosters" has been proposed in Japanese Patent Publication No. 140340/85 published July 25, 1985 and in Japanese Patent Publication No. 222241/87 published Sept. 30, 1987. In Publication No. 140340/85, it is alleged that any amino compound can be utilized as an "incorporated booster", while Publication No. 222241/87 is directed to use as "incorporated boosters" of amino compounds defined by a specific structural formula. Publication No. 222241/87 points to some of the problems involved in following the teachings of Publication No. 140340/85 including problems relating to leaching of the amino compounds from the element during development and the generation of "pepper fog".
A photographic system depending on the conjoint action of hydrazine compounds which function as "nucleators" and amino compounds which function as "boosters" is an exceedingly complex system. It is influenced by both the composition and concentration of the "nucleator" and the "booster" and by many other factors including the pH and composition of the developer and the time and temperature of development. The goals of such a system include the provision of enhanced speed and contrast, together with excellent dot quality and low pepper fog. It is also desired that the amino compounds utilized be easy to synthesize, low in cost, and effective at very low concentrations. The prior art proposals for the use of amino compounds as "boosters" have failed to meet many of these objectives, and this has seriously hindered the commercial utilization of the system.
It is toward the objective of providing improved methods and elements utilizing certain amino compounds as "incorporated boosters", which overcome many of the disadvantageous features of the prior art, that the present invention is directed.